Light-emitting diode and a method for manufacturing the same

ABSTRACT

A method for manufacturing a light-emitting diode (LED) is provided. The method includes following steps. A LED wafer including a substrate and a plurality of light-emitting units formed thereon is provided. At least a portion of the substrate is removed. The LED wafer is fixed on an extensible membrane, wherein the light-emitting unit faces the extensible membrane. The LED wafer is broken to form a plurality of LED dices separated from each other, wherein each LED dice includes at least one light-emitting unit. The extensible membrane is expanded to make a distance between any two of the LED dices become larger.

This application is a continuation application of application Ser. No.15/045,440, filed on Feb. 17, 2016, now U.S. Pat. No. 9,728,672, whichclaims the benefit of U.S. provisional application No. 62/116,923, filedon Feb. 17, 2015, and the benefit of Taiwan application No. 104123854,filed on Jul. 23, 2015, the contents of which are incorporated herein byreference.

TECHNICAL FIELD

The disclosure relates in general to a light-emitting diode (LED) and amethod for manufacturing the same, and more particularly to an LEDmanufactured by grinding, cutting, and breaking an LED wafer and amanufacturing method thereof.

BACKGROUND

According to the generally-known method of manufacturing an LED,firstly, a light-emitting element is formed on the epitaxy of asubstrate, wherein the light-emitting element comprises an n-typesemiconductor layer, a light-emitting layer and a p-type semiconductorlayer. The substrate and the light-emitting element together form an LEDwafer. Then, one surface of the LED wafer having the light-emittingelement is fixed on a crafting table using a liquid wax having adhesion.Then, the other surface of the substrate opposite to the light-emittingelement is grinded until the substrate reaches a predetermined smallerthickness. Then, the LED wafer is removed from the crafting table, andthe LED wafer is further cut and separated to obtain a plurality ofLEDs.

After the LED wafer is removed from the crafting table, the LED wafermay easily become warped due to residual stress. Furthermore, since thesubstrate becomes thinner after grinding, the warping effect caused byresidual stress becomes more apparent. Additionally, the substrate beingtoo thin may easily end up with breakage or damage. Particularly, duringthe cutting process, the wafer may be easily broken or damaged.Therefore, the generally known manufacturing method of LED still needsto be improved.

SUMMARY

The disclosure is directed to a light-emitting diode (LED) and amanufacturing method thereof capable of increasing product quality andavoiding wafer warpage and substrate breakage.

A method for manufacturing a light-emitting diode (LED) in the presentdisclosure includes following steps. A LED wafer including a substrateand a plurality of light-emitting units formed thereon is provided. Atleast a portion of the substrate is removed. The LED wafer is fixed onan extensible membrane, wherein the light-emitting unit faces theextensible membrane. The LED wafer is broken to form a plurality of LEDdices separated from each other, wherein each LED dice includes at leastone light-emitting unit. The extensible membrane is expanded to make adistance between any two of the LED dices become larger.

A method for manufacturing a light-emitting diode (LED) in the presentdisclosure includes following steps. A LED wafer including a substrateand a plurality of light-emitting units formed on the substrate isprovided. At least a portion of the substrate is removed. A fixing pieceis pasted on a surface of the LED wafer. The LED wafer is fixed to anextensible membrane, wherein the light-emitting unit faces theextensible membrane, and the LED wafer is disposed between the fixingpiece and the extensible membrane, and the fixing piece, the LED waferand the extensible membrane form a complex. The LED wafer is broken inthe complex to form a plurality of LED dices. The fixing piece isremoved from the complex to remain the LED dices disposed on theextensible membrane. The extensible membrane is expanded to make adistance between any two of the LED dices become larger.

The advantage of the disclosure is that before the LED wafer is removedfrom the crafting table, the fixing piece is firstly pasted on the LEDwafer to provide a supporting force to the LED wafer to maintain theflatness of the wafer and avoid the wafer being warped due to residualstress. Furthermore, the fixing piece helps to enhance the structuralstrength of LED wafer and avoid the substrate being broken or damaged,such that the quality and reliability of the manufactured products canbe increased. Additionally, through the design of suitable thicknessratio between the elements (such as 2-20 times exemplified above) orsuitable beam-divergence angle, the LED can achieve bettercentralization effect of the light, and is advantageous to the situationrequiring the light to be centralized.

The above and other aspects of the disclosure will become betterunderstood with regard to the following detailed description of thepreferred but non-limiting embodiment (s). The following description ismade with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an LED wafer;

FIG. 2 is a flow diagram of a manufacturing method of LED according toan embodiment of the disclosure;

FIG. 3 is a schematic diagram of partial steps of the manufacturingmethod according to an embodiment of the disclosure;

FIG. 4 is a schematic diagram of remaining steps of the manufacturingmethod according to an embodiment of the disclosure;

FIG. 5 is a schematic diagram of an LED according to an embodiment ofthe disclosure;

FIG. 6 is a relationship chart of light intensity versus radiationangle.

In the following detailed description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of the disclosed embodiments. It will be apparent,however, that one or more embodiments may be practiced without thesespecific details. In other instances, well-known structures and devicesare schematically shown in order to simplify the drawing.

DETAILED DESCRIPTION

Referring to FIGS. 1-4, the manufacturing method of LED according to anembodiment of the disclosure includes following steps:

Step 11: an LED wafer 2 is provided, wherein the LED wafer 2 includes asubstrate 21, and a light-emitting unit 22 covering the substrate 21.The substrate 21 can be a sapphire substrate, a gallium nitride (GaN)substrate, an aluminum nitride (AlN) substrate, a silicon substrate, ora silicon carbide (SIC) substrate. The substrate 21 is not limited toany specific type of substrate but is exemplified by a sapphiresubstrate in the present embodiment. The substrate 21 has a thicknessaround 430 μm, and has a first side 211 and a second side 212 oppositeto the first side 211.

The light-emitting unit 22, disposed on the first side 211 of thesubstrate 21, has an n-type semiconductor layer 221 disposed on thefirst side 211, a p-type semiconductor layer 222 disposed above then-type semiconductor layer 221 at an interval, and a light-emittinglayer 223 interposed between the n-type semiconductor layer 221 and thep-type semiconductor layer 222. Let the GaN LED be taken for example.The n-type semiconductor layer 221 and the p-type semiconductor layer222 can be formed of an n-type GaN material and a p-type GaN material,respectively. The light-emitting layer 223, also referred as the activelayer, can be formed of a multiple quantum well (MQW) structure. Thelight-emitting layer 223 can be formed of a material such as GaN, indiumgallium nitride (InGaN), or aluminum gallium nitride (AlGaN). However,in the implementation of the present embodiment, the material of eachlayer of the light-emitting unit 22 is not limited to any specificrestrictions. Besides, the LED wafer 2 further includes an electrode notillustrated in the diagram but connected to the light-emitting unit 22to transmit an external power to the light-emitting unit 22, whichconverts an electric energy into an optical energy. Since the electrodeis not the focus of improvement in the disclosure, detailed descriptionsof the electrode are not disclosed here.

Step 12: the LED wafer 2 is processed by way of grinding until thesubstrate 21 has a thickness smaller than or equal to 100 μm.Preferably, the thickness is smaller than or equal to 50 μm. To be morespecific, in the present step, the first side 211 of the substrate 21faces downward and the second side 212 faces upwards, and a liquid waxhaving adhesion is coated on a surface of the light-emitting unit 22 forfixing the LED wafer 2 on a crafting table 3. The present step is alsoreferred as the waxing step. Then, the second side 212 of the substrate21 can be grinded by a grinder and then polished by a polisher until thesubstrate 21 has a thickness smaller than or equal to 100 μm.

Step 13: a fixing piece 4 is pasted on a surface of the LED wafer 2. Thefixing piece 4 of the present embodiment is a sheet whose surface hasviscose and adhesion. The fixing piece 4 is adhered on the surface ofthe substrate 21 facing upwards.

Step 14: the LED wafer 2 is washed using a liquid such as acetone (ACE)or isopropanol (IPA) to dewax the surface of the LED wafer 2 facing thecrafting table 3, and the LED wafer 2 is detached from the craftingtable 3. The present step is also referred as the dewaxing step.

Step 15: the LED wafer 2 is fixed on an elastic membrane 5 (alsoreferred as the blue film) which is surrounded by an expansion loop 51.One surface of the LED wafer 2 having the light-emitting unit 22 facesthe elastic membrane 5, and the other surface of the LED wafer 2 havingthe fixing piece 4 faces outwards.

Step 16: the LED wafer 2 together with the fixing piece 4 are cut andbroken, such that the LED wafer 2 forms a plurality of LEDs 20.Specifically, the LED wafer 2 is cut into a plurality of blocks by wayof laser scribing according to a predetermined size. Then, by applyingan instant impact on the LED wafer 2 along the trace of the cuttingline, the blocks will separate from each other to form a plurality ofLEDs 20. The present step is also referred as the breaking step.

Step 17: a UV light is projected on the fixing piece 4 to decompose theviscose, and then the fixing piece 4 is peeled from the LEDs 20.

Step 18: the elastic membrane 5 is pulled outwards and expanded towardsthe radial direction (such as the arrow direction indicated in the laststep of FIG. 4) by an expander not illustrated in the diagram, such thatthe LEDs 20 are separated from each other as the elastic membrane 5expands. After the expansion step is completed, a certain distanceexists between adjacent LEDs 20, such that the LEDs 20 can be easilyremoved from the elastic membrane 5 one by one. Referring to FIG. 5,each of the LEDs 20 manufactured using the manufacturing method of thedisclosure and the LED wafer 2 in FIG. 1 have different sizes but bothinclude the same layers. That is, both include a substrate 21, an n-typesemiconductor layer 221, a p-type semiconductor layer 222 disposed abovethe n-type semiconductor layer 221, and a light-emitting layer 223interposed between the n-type semiconductor layer 221 and the p-typesemiconductor layer 222.

In the disclosure, the thickness of the substrate 21 is reduced to besmaller than or equal to 100 μm. Or, the thickness of the substrate 21is even reduced to be smaller than or equal to 50 μm in anultra-thinning process, such that the LED 20 can be miniaturized orthinned. Before the LED wafer 2 is removed from the crafting table 3(that is, before the dewaxing step), the fixing piece 4 can be pasted onthe LED wafer 2 to provide a supporting force to the LED wafer 2 tomaintain the flatness of the wafer and avoid the wafer being warped dueto residual stress. Moreover, the fixing piece 4 helps to enhance thestructural strength of the LED wafer 2 and avoid the LED 20 being brokenor damaged. For example, during the cutting step of the wafer, thebreakage problem can be avoided, and the quality and reliability of theproducts can be increased. Furthermore, in the present embodiment, theUV light projected on the fixing piece 4 can decompose the viscose onthe fixing piece 4, such that the fixing piece 4 can be peeled easily.The present removing step is simple and easy to implement.

Referring to FIG. 5, in terms of the structural design of the LED 20 ofthe disclosure, the thickness of the substrate 21 being 20-100 μm can be2-20 times (preferably 5-10 times) larger than the thickness of thelight-emitting unit 22. When the thickness ratio is 2-20 as describedabove, the light emitted from the LED 20 can be better centralized andgenerate a smaller output angle which is advantageous to the situationwhen the flash light of a mobile phone is used. Besides, when the ratioof the thickness of the substrate 21 to the thickness of thelight-emitting unit 22 is too large, the thinning design will bedisadvantaged. Therefore, the ratio range disclosed above is a preferredrange.

The range of the beam-divergence angle of the LED 20 preferably isbetween 115°-140°, and more preferably is between 115°-130°. Within therange of the beam-divergence angle, the light can be better centralized,and such design is advantageous to the situation requiring the light tobe centralized. Moreover, the range of the beam-divergence angledisclosed above goes with a suitable thickness of the substrate 21.Referring to FIG. 6, the beam-divergence angle can be obtained throughfollowing ways. A relationship chart of light intensity versus radiationangle can be obtained from the light intensity distribution of the LED20. The angle corresponding to a half of the maximum light intensity isthe beam-divergence angle of the LED 20. As indicated in FIG. 6, whenthe thickness of the substrate of the LED varies, the correspondingbeam-divergence angle also varies accordingly. Table 1 illustrates anumber of corresponding relationships between substrate thickness andbeam-divergence angle.

TABLE 1 Substrate thickness 30 μm 50 μm 150 μm 220 μm 300 μm 400 μmBeam- 126° 131° 142° 146° 147° 148° divergence angle

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the disclosed embodiments.It is intended that the specification and examples be considered asexemplary only, with a true scope of the disclosure being indicated bythe following claims and their equivalents.

What is claimed is:
 1. A method for manufacturing a light-emitting diode(LED), comprising: providing a LED wafer comprising a substrate and aplurality of light-emitting units formed thereon; removing at least aportion of the substrate; fixing the LED wafer on an extensiblemembrane, wherein the light-emitting unit faces the extensible membrane;breaking the LED wafer to form a plurality of LED dices separated fromeach other, wherein each LED dice comprises at least one light-emittingunit; and expanding the extensible membrane to make a distance betweenany two of the LED dices become larger, wherein a fixing piece is pastedon a surface of the substrate before the step of fixing the LED wafer onthe extensible membrane, and the LED wafer is broken together with thefixing piece to form the LED dices.
 2. The method according to claim 1,further comprising removing the fixing piece after breaking the LEDwafer.
 3. The method according to claim 1, wherein the step of removingthe portion of the substrate comprises a grinding step and a polishingstep.
 4. The method according to claim 1, further comprising a waxingstep for adhering the LED wafer to a crafting table.
 5. The methodaccording to claim 4, further comprising a dewaxing step for detachingthe LED wafer from the crafting table.
 6. The method according to claim1, wherein the step of removing the fixing piece is implemented byirradiating a UV light on the fixing piece to decompose a viscose on thefixing piece and then removing the fixing piece from the LED dices. 7.The method according to claim 1, wherein after the step of removing theportion of the substrate, the substrate has a thickness 2-20 timeslarger than a thickness of the light-emitting unit.
 8. The methodaccording to claim 1, wherein after the step of removing the portion ofthe substrate, the substrate is thinned down to have a thickness smallerthan or equal to 100 μm.
 9. The method according to claim 1, whereinbefore the step of breaking the LED wafer, the LED wafer is cut into aplurality of blocks by way of laser scribing.
 10. The method accordingto claim 1, wherein a range of the beam-divergence angle of the LEDdices is centralized between 115°-140° after the step of removing theportion of the substrate.
 11. The method according to claim 10, whereina range of the beam-divergence angle of the LED dices is centralizedbetween 115°-130° after the step of removing the portion of thesubstrate.
 12. A manufacturing method of light-emitting diode (LED),comprising: providing an LED wafer comprising a substrate and alight-emitting unit formed on the substrate; removing at least a portionof the substrate; pasting a fixing piece on a surface of the LED wafer;fixing the LED wafer to an extensible membrane, wherein thelight-emitting unit faces the extensible membrane, and the LED wafer isdisposed between the fixing piece and the extensible membrane, and thefixing piece, the LED wafer and the extensible membrane form a complex;breaking the LED wafer in the complex to form a plurality of LED dices;removing the fixing piece from the complex to remain the LED dicesdisposed on the extensible membrane; and expanding the extensiblemembrane to make a distance between any two of the LED dices becomelarger.
 13. The method according to claim 12, wherein the step ofremoving the portion of the substrate comprises a grinding step and apolishing step.
 14. The method according to claim 12, further comprisinga waxing step for adhering the LED wafer to a crafting table and adewaxing step for detaching the LED wafer from the crafting table. 15.The method according to claim 12, wherein the step of removing thefixing piece is implemented by irradiating a UV light on the fixingpiece to decompose a viscose on the fixing piece and then removing thefixing piece from the LED dices.
 16. The method according to claim 12,wherein after the step of removing the portion of the substrate, thesubstrate has a thickness 2-20 times larger than a thickness of thelight-emitting unit.
 17. The method according to claim 12, wherein afterthe step of removing the portion of the substrate, the substrate isthinned down to have a thickness smaller than or equal to 100 μm. 18.The method according to claim 12, wherein before the step of breakingthe LED wafer, the LED wafer is cut into a plurality of blocks by way oflaser scribing.
 19. The method according to claim 12, wherein a range ofthe beam-divergence angle of the LED dices is centralized between115°-140° after the step of removing the portion of the substrate. 20.The method according to claim 19, wherein a range of the beam-divergenceangle of the LED dices is centralized between 115°-130° after the stepof removing the portion of the substrate.